Portable electrically-driven tool.



J. A. OSBORN.

PORTABLE ELEGTRIGALLY DRIVEN TOOL.

APPLoATIoN FILED 13110.12. 1913.

1,1 1 '7, 140. Patented Nov. 10, 1914.

All"

JOSEPH A. OSBOBN, OF ST. LOUIS, MISSOURI.

PORT-ABLE ELECTRICALLY-DRIVEN TOOL.

Specification o! Letters Patent.

Application led December 12, 1913. Serial No. 806,181.

To all whom it may concern:

Be it known that I, JOSEPH A. OsBoRN, a citizen of the United States, and residing at St. Louis, inthe State of Missouri, have invented certain new and useful Imjrovements in Portable Electrically-.Driven o ols, of which the following is a specification.

This invention relates to portable elec tricallyv operated tools, such as, drills and reamers. Such a tool is provided with an electric motor comprising a stator and a rotor, and the rotor drives a tool element, such as, a drill or reamer. As the electric motor necessarily operates at a high speed, gearing is provided to reduce the speed of the tool element to the desired point. The counter-shaft of the reduction gearing is, of course, mounted eccentrically with respect to the tool element, and thisgives the armature a considerable leverage tending to rotate the stator. The stator is provided with a handle or grip to permit the operator to guide the same, and in case of tools of large capacity is usually provided with one or more torsion arms, projecting radially with respect to the stator, to permitthe operator to-hold the stator against rotary movement, due to the reaction caused by the'tool element holding rotor. It sometimes happens that theA tool element will bind or stick in the work operated upon; when this happens the stator will tend to revolve in a direction opposite to the direction df rotation of the rotor, the countershaft and itsl connected ears rotating and rolling around the tooI and acting as planetary gears, and causing the armature to act at a considerable leverage. Since the leverage is great, and since the rotor was at that vtime-revolving at a high s eed, the statorl will be started with a jer This sudden starting of the stator is not only liable-to. throwthe operator oi ofvhis feet, but is also liable to seriously injure him. v

.It has been proposed to overcome this objection-by' providing a' switch, which will be opened by the operator when the stator 'starts to revolve upon binding of the tool qvfelement, so" as to break the motor circuit, that is disconnect the motor from its source otfcurrent. "In large `capacity or heavy duty t0o`ls,however, (weighing as muchas ninety .,:pounds,and having. a four ,horse 66 poiles lmotor, developing the torque. of an rotor has considerable inertia, and this rotor rotating at a high speed accumulates considerable momentum, so that, even after the current is cut 0H, this rotor, operating under its momentum yand at a considerable leverage on the stator, tends to revolve the stator with considerable force when the tool element sticks. Moreover the heavy stator, and especially the radially projecting arms, possessl considerable inertia, whereby this stator and vits arms, when started by the binding of the tool, will accumulate considerable momentum, and will therefore continue to revolve under momentum. The result, therefore, is that, upon sticking of the tool element, and afterthe current is cut ofi, the stator will be started and continue to revolve with lconsiderable force due to the accumulated momentum, and the stator and its arms are liable to cause considerable injury to the operator before the energy due to inertia is dissipated. v

The objects of this invention 'therefore are to provide means for braking the stator with respect to its rotor, so as to dissipate the energy and bring the stator tov rest,and more particularly to provide electrical braking means set in operationby the operator upon binding ofthe tool element, ior causing the braking means to be applied, so as to arrest the stator with respect tothe rotor immediately after the tool starts to bind.

Further objects will appear from4` the detail description taken in connection with the accompanying drawing in which;

Figure 1 is a vertical section throu h a tool embodying this inventiom'oneo Q the torsion arms being shown in elevation, Fig. 2 is a horizontal section, taken along a part of one of the torsion arms, Fig. frs a verratentea Nov. 1o, 1914.

l eight horse power motor at starting) the l tical section, Fi 4 is an'enlarged hori -v zontal section, ta en along another part of the arm, showin the switch, F ig. 51s a vertical section, `big. 6 is a section .ou the line 6-,6 Fig.l l, Fig. 7 `is a detail showing the resistance element, Fig. 8 is a.y diagram, showing Athe connections ofv the motor and jthe braking resistance with the switch, Eiga..

19 is a diagram, showing the connections gi th'e motor" when running, andj1 ig. 1s a diagram, showing the connections of the motor lwhen braking..

l Reife-ing tothe @warranties ies pole type.

a pin and slot connection with a linlr 39 10 designates a stator casing carrying radially projecting armsA 12 and 13. This stator also carries the field poles 14 provided with a magnetizing'winding F of the usual multi- The rotor or armature is mounted in the stator and is provided with a winding A. The rotor shaft 17 is provided with gear teeth 18 meshing with a gear 19 on a counter shaft, which is in turn provided 10 with gear teeth 2O meshing with a gear 21 on a spindle 22, carrying the tool element 23.

The arm 13 has an enlarged portion 30 forming a receptacle closed by a cap 31. This receptacle receives a switch, which is i5 of the three pole, double throw type, and

comprises a base 32 provided with contacts 33 and 34, and a movable'switch element havingblades 35 mounted on a shaft 39. This shaft 39 has an arm 38 connected by on a plunger 40 guided in the arm 13. AThe plunger 40 has attached thereto a cross head 41, which has a pin and slot connection with a'sliding bar 42, having a limited pivotal movement on trunnions 36 bearing on the inside face of the arm. This bar has recessed shoulders 43-I-44 coperating with crossbars 45--46 in the arm. A hand piecev 47 is pivoted in the arm, and is connected by a spring '48 to the bar. 'lli-spring 49 .for dynamic braking,

connects this handle with an end plug 50 in the arm.' When'the hand piece 47 is in the position shown in the drawing, the switch element will be in a position to hold the blades 35 in engagement with the contacts l34. lf now the hand piece is released, the spring 49 will swing this hand piece so as to move the spring 43 over the center of the hand piece, and, iirst, place the bar. 42

under the tension so as to tend to move it to the left, and then tip the left hand endl of the fbar downwardly so as to move the shouldered recess 44 out of engagement with the cross bar 46, and cause the entire bar to be moved to the left under the tension of the spring 49. This will disengage the blades 35 from the contacts 34 and throw them into engagement with the contacts 33. lt will be noted that the-bar 42 is under the tension of 50 the lspring 48 before the shouldered recess 44 is disengaged from the'bar'46; therefore after this bar is tipped it will move to the left with la snap, thereby quickly shifting the movable switch element. Similarly the switch can be moved to its rstposition by movin the hand piece back against the tension oi itsl spring 48. The `line connections to the switch vare shown. at 51. The above described 4switch actuating mechanism is 6G well lmown and forms no part of this, in-

vention.

The arm 12 has mounted therein a resistance element 55, comprising a core 56 of insulating material, having Va resistance t5 l winding lt, and provided with binding posts 58, 59, 60 and 61, connected to different parts of the winding as shown in Fig. 7. The core is also provided with an aperture 62 to receive a lead 63. The lead 63 4and the end lead 64 of the winding are connected to the switch, the connections being shown in Fig. 8, which also shows the connections of the armature and iield windings to this switch. The lead 63 can be connected to any of the binding posts Ato cut in diiferent parts of the winding R. The resistance element is inclosed by a sleeve 65 of insulating material, and the entire element is rendered accessible by unscrewing the arm 12 from the stator.

When the switch is in position as shown in the drawing, so as to connect the blades 35 with the contacts 34, the field and armature will be connected in series with the line to cause the motor to operate as a series motor, as shown in Fig. 9. lf the switch is now thrown to reverse position, so as to conneet the switch blades 35 with the contacts 33, the motor will, first, bel disconnected from the line, and the armature and eld will then be connected in series with the resistance R, the iield terminals. being, however, in this case reversed withirespect to the armature, as shown in Fig. 10.

ln Fig. 10, the motor is shown connected at which time the motor acts as a generator. To do this it is necessary to connect the series held F in series with the armature, but in'reversed relation, in order that the polarity of the ield may 'remain unchanged, as the direction of current is reversed by changing the machine from motor to generator. A resistance must also be cut in to provide a suitable load and limit the value of the current. noted that the spring 49 will normally throw the switch to the position in which the connections will be made as shown in Fig. 10,l and that the running connections are made while the hand piece 47 is held in the position shown in Figs. 1 and 3,

Vagainst the tension of the spring 49. When however, this hand piece is released it will be automatically returned by the spring 49.

To start the motor the operator will move the hand piece 47 to the position shown in Figs. 1 and 3, and hold it in that position llO ila

while the hand grips the arm 13. This will Y throw the switch to running position, in which the motor is connected to the line to operate as a series motor-,as shown in `Fig. 9. lf now thev tool should bind, the stator will start to revolve with a jerk, and as it starts the operator is compelled to release his grip on the handle, which will causethe spring 49 to return the hand-piece 47, so as to throw the switch to its other position; This movement of the switch will first 'disl connect the motor from the -line,'and will then connect the motor armatureA in with the resistance R and the field winding F, with the field winding in reversed relation. The revolving of the rotor and stator,

. relatively under momentum will now cause effect will vary with the speed and with the resistance of the dynamic braking circuit. By ro er adjustment of the resistance R, the raliing effect can be made great enough to arrest the stator immediately upon binding ofthe tool. As the relative movement between the rotor and stator decreases, the current will decrease with the speed to zero. It will therefore be Seen that the invention accomplishes its objects. As soon as the tool element starts to bind, the operator will automatically throw the switch to disconnect the motor from the line, and the braking means will then be applied to automatically bring the stator to a stop. This braking means consists in this case of the motor together with its controlling means. The additional partis added to the tool are very simple and of light weight. This point is important in portable tools, Where the weight 'must be kept down to a' minimum. The use of the motor itself as a brake requires the addition of only a switch and a resistance, neither of which effects the construction of the tool as a Whole, and does not complicate either its construction or operation.

While I# have described and shown one form off braking means which may be used with an electrically opera-ted portable tool, it is obvious that other braking means may be used. Thus the brake may be a mechanil cal friction brake, which is setgby a spring and released by a solenoid in the motor circuit, so that when themotor is connected to the line, the solenoid will receive current at the same time to release the'brake, so as to allow the rotor to start. As soon, however, as the inotor is disconnected from the line bythe operator releasing his hold 'on the hand piece, the solenoid will be cut out with the motor, permitting the spring to apply the brake and stop the motor. It is also obvious that various other arrangements may be used wherebya current may be passed through the motor circuit in such a lmanner as to cause a resistance to rotation and brake the stator With respect to the rotor, so as to arrest the movement of the former. It is further obvious that various -changes may be made in details of construction Without departing from the ,spirit -o this invention, and it is therefore to be understood that this invention is not to be liixiitad to the specic construction and operation described.

Having thus described is claimed is:

l. A portable electrically operated tool having an electric driving motor constructed to acquire considerable momentum and including a tool element driving rotor and a manually held stator, and means for braking said stator with respect to said rotor, adapted to prevent rotation of the stator upon binding of the tool element.

2. A portableelectrically operated tool having an electric driving motor including a tool element driving -rotor and a stator, and means operating upon binding of the tool-element for brakingv said stator with respect to said rotor.

3. A portable electrically operated tool having an electric driving motor constructed to acquire considerable momentum and including a tool element driving rotor and a manually held stator, and means for disconnecting the motor from the source of current and for then braking said stator with respect to said rotor, adapted to prevent rotation of the stator upon binding of the tool element.

4. A portable electrically operated tool having an electric driving motor constructed to acquire considerable momentum and including a. tool element driving rotor and a manually held stator, and means for disconnecting the motor from the source of current and forv then causing current to traverse the motor to brake said stator with respect to said' rotor, adapted to prevent rotation of the stator upon binding of the tool element.

5. A portable electrically operated tool having an electric driving motor constructed to acquire considerable momentum and including a tool element drivingrotor and a manually held stator, and means for disthe invention what connecting the motor from the source of current and for then connecting the motor to dynamically brake said stator with respect to said rotor, adapted to prevent rotation of the stator upon binding of the tool element.

6..A portableelectrically operated tool having an electric driving motor including a tool element driving rotor and a stator, and means operated upon binding of the tool element for causing a current to traverse the motor to brake said stator with respect to said rotor.

7 A portable electrically operated tool having an electric driving motor including a tool element driving rotor and a stator, and means operated upon binding of the tool element for disconnecting the motor from the source of current and for then braking said stator with respect to said rotor.

8. A portable electrically operated tool having an electric driving motor including a tool element driving rotor and a stator, and means operated upon binding of the ,tool

element for disconnecting the motorvfrom I having an electric driving motor constructthe source of current and for then connecting the motor to dynamically brake said stator with respect to said rotor.

9. A portable electrically operated tool having an `electric driving motor including a tool element driving rotor and a stator,

f means for braking said stator Wlth respect to said rotor, and means set in operation by the operator upon binding of the tool `element for setting said braking means. f

10. A portable electrically. operated tool having an electric driving motor including a tool element driving rotor and a stator, means for braking said stator With respect to said rotor, and means set in operation'by the operator upon binding of the tool element for disconnecting the motor from the source of current and for then setting said braking means.

11. A portable electrically operated tool having an electric driving motor including a tool element driving rotor and a stator,'and means set in operation by the operator upon binding of the tool element for causing a current to traverse the motor to brake'said stator lWith respect to said-rotor.

12. A portable electrically operated tool having an electric driving motor including a tool element driving rotor and a stator, and means set in operation by the operator upon binding of the tool element for disconnecting the motor from the'source of current and for then connecting the motor to dynamically brake said stator with respect to said rotor. l

13. A portable electricallyoperated tool having an electric driving motor includingl a tool element driving rotor and a stator, and having a torsion arm for holding the stator, means for braking said stator with respect to said rotor, and a controlling member for said braking means mounted on said arm.

14. A portable electrically operated tool having an electric driving motor including' a tool element driving rotor and a stator, and having a torsion arm for holding the stator, means for braking said stator with respect to said rotor and means on said arm set inoperation by the operator upon binding ofthe tool element for setting said braking means. y

15. A portable electrically operated tool having an electric driving motor including a tool element drivingJ rotor and a stator, and having a torsion arm for holding the stator, and a resistance for the motor circuit, positioned in said arm.

16. A portable electrically operated tool ed to acquire considerable momentum and including a rotor and a manually held stator, a rotatable tool element, gearing mounted on said stator and connecting said rotor and said tool element, and means for braking said stator with respect to said rotor, adapted to prevent rotation of the stator upon binding of the tool element.

17. A portable electrically operated tool having an electric driving motor constructed to acquire considerable momentum and including a rotor and a. manually held stator, a rotatable tool element mounted in said stator separately from but driven by said rotor, and means for braking said stator with respect'to said' rotor, adapted tov prevent rotation of the stator upon binding of the tool element.

18. A portable electrically operated tool having an electric driving motor constructed to acquire considerable momentum and including a rotor and a rmanually held stator, a rotatable tool element, gearing mounted on said stator and connecting said rotor and said tool element, one-element of said gearing being eccentric with respect to said rotor, and means for braking said stator with respect to said rotor, adapted to prevent rotation of the stator upon binding of the tool element.

. 19. A portable electrically operated tool having an electric driving motor including a rotor and a stator, and having a torsion arm for holding the stator, a rotatable tool element, gearing connecting said rotor and said tool element, means for braking said stator With respect to said rotor, and a controlling member for said braking means mounted on said arm.

Josnrn A.. osnonjn.

Witnesses: 'l 1 GERTRUDEA. HEYMANN, J. H. vBironnma. Y 

